So I read this BL manga about a high school student who went to dye his hair(? and the hairstylist was kind of his friend. The MC was down cause he had a crush on his classmate (that later on resulted being the hairstylist´s younger brother) but somehow the MC and the stylist became f*ckbuddys. I remember the stylist having a huge apartment and that he had a relationship with an older dude that appeared in the middle of the story, he was married and kind of a sadist (he´s the one that gifted the apartment to the stylist). The MC helps him get out of that relationship, and all the romance appeared as usual(?
But what I do remember the most is the final notes of the manga where the mangaka solved all the questions about the stylist´s past cause it was barely explained in the chapters, that he was kicked out of his house and that he started the relationship with the married guy when he was really young. All of this in a pink-kind of fond letter.